“…Accordingly, social stimuli have been shown to entrain endogenous rhythms ( Mistlberger and Skene, 2004 ; Favreau et al, 2009 ; Bloch et al, 2013 ) both in species with limited access to the main environmental time cue, i.e., the LD cycle, or those living on natural LD cycles. For example, the circadian synchronization of marmosets placed in temporal isolation (i.e., constant light condition) is favored by the activity profile ( Melo et al, 2013 ) or vocalizations ( da Silva et al, 2014 , but see Erkert et al, 1986 ) of conspecifics, or acoustic and olfactive contact between reproductive pairs ( Bessa et al, 2018 ). In humans, the evidence suggests that social signals are weaker than light cues, but both jointly influence the circadian response (i.e., rhythms with cycles of approximately 24-h) ( Davidson and Menaker, 2003 ; Mistlberger and Skene, 2004 ).…”